MicroRNA profiling of gastric content from breast-fed and formula-fed infants to estimate last feeding: a pilot study.

Recently, we were consulted about a challenging case, where an infant died by poisoning and the drug-dependent mother insisted that she unintentionally gave the toxic drug through breast milk. Accordingly, we investigated the utility of immunoblotting and microRNA (miRNA) profiling of the infant's gastric content (GC) to differentiate between breast-feeding and formula-feeding. As a pilot study, we sampled the GC from breast-fed (GCB) and formula-fed (GCF) infants, as well as gastric juice (GJ) from fasted adults at autopsy. Breast milk (BM) samples were collected from volunteers within 1 year post-delivery. By immunoblotting, lactoferrin and gross cystic disease fluid protein (GCDEP) were clearly detected in BM, but could not be detected in GCB. Similarly, β-lactoglobulin was detected in formula milk, but could not be detected in GCF. Meanwhile, miRNA sequencing revealed that the miRNA expression profile of GCB was closer to BM than GCF and GJ. Especially, miR-151a and miR-186 were more abundant in BM and GCB than in GCF and GJ. Our study is the first to elucidate the human GJ miRNA profile and demonstrate the possibility that miR-151a and miR-186 in GC may be the biomarker of breast-feeding.